It can be a slight difference, but not necessarily. If you go to the store and see someone you know, then their spouse comes up to you and is looking for them, you can reply "I saw him a while ago". Which would mean within the time you are in the store...which isn't a very long time.
"a while ago" is a different time frame that is farther back in time than "recently" which is more like "a little bit ago". It is also used as a vague reference in which it could also cover this, but it would then be that "a while ago" could include the translation to Spanish of "poco" and not that "poco" would always mean "a while ago".
"Yo lo vi en este momento." might be better for "I saw him just now." which is similar to "I saw him a moment ago."
"Yo lo vi recientemente." can also be "I saw him recently."
"Yo lo vi hace un rato." is perhaps better for "I saw him a while ago."
For "Yo lo vi hace poco.", we could also say "I saw him not long ago." or "I saw him a little bit ago.", but I don't know if those are accepted. I think it is a bit more vague than "just now" which is even closer to the present and less vague than "a while ago" which can be a longer time from the present. On second thought, "not long ago" is rather vague and might cover "a while ago" also. Someone further down has said that "a little while ago" is accepted which makes more sense to me than "a while ago"as it is more specifically recent.
Here Spanish uses "hace poco" to define reciente for time: http://dictionary.reverso.net/spanish-definition/recientemente
Nake 89: You would need an "a el" in the sentence to be positive that the direct object (lo) is a male person i.e. him. Without that the sentence, one can correctly translate to "it" (as DL has done) or you can go out on a limb and assume that the "lo" is a male person., but without the "a el" we truly don't know.
I like that site. And I truly like their honesty. Straight and to the point. They said in your link above "The following verbs are irregular in the preterite and must be memorized:" At least it let's me know there are no shortcuts in this instance. Just buckle down and memorize them
Roll your mouse over "vi" and you will have the hover hints. Click on the blue tab to see the conjugation list. On my computer it does show present and past. It depends. As you come across new forms, they are added to the list. So, I don't have future yet and I remember that it used to be only the present.
This blue tab is not there now, however they have enlarged the list of hints for this word and for those who have the "Words" tab, you can access the conjugation of Ver. If not, here is a full conjugation of which you should pay attention to the "preterito perfecto simple":
A year later and I can click on the verb to see the list of conjugations.
This is my first time seeing 'hace poco' and got it wrong on the hear and write. I put 'asi'. Anyway in the sentence 'vi' is past tense for 'I saw' Right? Then "lo' is the direct object pronoun for him/it. There is no need for 'el' (meaning he and sometimes him). So, the sentence is lo=him/it; vi=i saw; hace poco= recently.
Only if further context is needed, otherwise it would be redundant. So basically, if you were having a conversation with somebody about somebody (masc.), if they are already aware of what or, in this particular case, who you are talking about, to say/add a él is unnecessarily redundant.
Señor Drakegta: I assume you are a native English speaker. We use verb tenses automatically. To you and me "I have seen" and "I saw" are identical. But when you are learning another language, you become hypersensitive to the verb tenses in the new language. So, in the sentence here, the verb tense is the preterite which in English is translated without auxiliary verbs because there are none when you read the sentence in Spanish.
https://en.wikipedia.org/wiki/Le%C3%ADsmo Duolingo is teaching Spanish used in South America and so does not include this variation at least not originally, perhaps to make sure we know which pronouns are which before dealing with dialect differences. I would not be surprised if they add "le" for some sentences to accomodate requests from Spaniards who are used to "leismo".
LO is the direct object pronoun: him, you (formal masculine) or it even when gender is not specified. SEE http://www.spanishcentral.com/translate/lo gives:
English Translation of LO (referring to masculine nouns)
1 : him, it
lo vi ayer I saw him yesterday
lo entiendo I understand it
2 (formal masculine) : you
disculpe, señor, no lo oí excuse me, sir, I didn't hear you
It can mean either "it" (as long as the noun it represents is masculine in Spanish), "him", or even stand for "usted" which would make it "you". "Lo entiendo." can mean "I understand "it." many times unless we were just talking about him, then it could mean "I understand him." or if you were just explaining something to me, then it could mean "I understand you." Again for the second two sentences, "I understand it." can often work too, meaning "I understand what he was talking about." or "I understand what you were talking about." So, that is the more common translation for that particular sentence. If we are talking about her, or something that is feminine in Spanish, then we would use "la". So the English "it" might be "lo" or "la" depending on which gender it is in Spanish, because everything is either masculine or feminine in Spanish.
"seldom" would mean "not often" and refers to a repetitive occurrence while this is about one occurrence which happened recently.
"hace poco" = "recientemente"
"a little bit ago", "a little while ago", or "recently"
We just need to learn their expression for "ago" which is "hace".