In this sentence it means "please".
In other sentences, it could be a conjugated form of the verb bitten, meaning "to request". For example: Ich bitte Sie, Geduld zu haben = "I ask (request) you to have patience".
If capitalised, it can also be a noun meaning "request". For example: Ich habe eine Bitte = "I have one request".
To be more precise, the skip function is available when you are starting a new skill. You click on the skill, and a rectangle pops out showing what level you've achieved in that skill, as well as how many lessons to the next level. On the right you'll see the "tips and notes" link represented by a light bulb symbol -- always read those -- and an option to test out of the skill (bringing you to the next level), represented by an icon of a key.
Are you used to "saying pls" or writing it? Hmmm... one can see that you are also used to not capitalizing the first letter of your sentences, nor the pronoun "I" and this all tells us you are more used to texting on your phone than reading books and good literature. It's not very complimentary to the impression one gets about your intellectual capacities. You might think about working on that, when you're not busy texting your bunny buddies.
do you say "Wasser" or use the other symbol that means the double "s" or does it not matter??
ss comes only after short vowels, ß only after long vowels and diphthongs.
Since the a in Wasser is short, only the spelling Wasser is correct.
Sometimes, the use of ss versus ß can make a difference in meaning: Bier in Massen trinken "drink beer in massive quantities" versus Bier in Maßen trinken "drink beer in limited quantities".
Usually, though, using the wrong spelling is simply wrong (e.g. there is no word Waßer or gross, and the spelling heissen is simply impossible since ei is a diphthong, not a short vowel).
That said: on Duolingo, you can replace ß with ss and write gross for groß (for the benefit of those who can't easily type the letter ß).
But when you're hand-writing German, you should remember the correct spelling.