Der Ort - is simply the location. A secondary meaning can be small village.
Der Platz - is best translated with place. There are some more meanings.
Triff mich auf dem Platz. - Meet me in the square.
Wir haben reservierte Plätze. - We have reserved seats.
Mach etwas Platz, bitte. - Make some room, please.
There is a special place in hell for you. - Für dich gibt es einen besonderen Platz in der Hölle.
"Dies" only works as an impersonal pronoun. Similar to "
"Dies ist schön." "This is beatiful." Similarly, "Das/Dies/Es ist der Mann."This/That/It is the man."
Notice how it does not agree with the gender of the man. "Das/Dies/Es" are also neuter. They are stand-ins for the subject, because grammar needs one. They don't refer to anything or anyone in particular, thus impersonal pronoun.
As an article "dies" always has to take an ending, -er, -e, es, -em or -en. Articles are directly connected to a noun like "dieser Platz".
"Dieser Platz ist schön." (By the way, "schön" does not get an ending because it is a predicative adjective with ist.)
"Dies*er schön*e Platz" "This beautiful place" (as an attributive adjective belonging to Platz is has to take an ending.)
"Dieser/diese/dieses" as standalone words not attached to a noun are personal pronouns (stand-ins for an established noun). Those keep their endings and translate to "this one" rather than to "this" (as the impersonal pronoun).
Bis jetzt waren alle Plätze hässlich. *Dieser ist schön./Up until now all places were ugly. This* one is beautiful.
Wow, thank you very much for taking the time to write this out! It makes perfect sense now, thanks a lot! :) I would give you a lingot, if I had one!
I don't quite understand why schön gets the ending -e, though. Sure, I understand why it has to, but what is the rule? Since Platz is masculinum, why isn't scönER? (From your example: Dieser schöne Platz)
You've touched one of the most confusing topics of German grammar here. In short, only one word gets the -r ending to mark masculine nominative singular. In this case, it is the article dieser. No -r left for schön. If you had used not a definite (der/die/das) type of article like dieser, but an indefinite article type (ein/eine/ein, kein/keiner/kein, mein/meiner/mein, ...) the -r would have been attached to the adjective.
Definite type article combinations: Dieser schöne Platz. Der schöne Platz. Jeder schöne Platz. Welcher schöne Platz? (This/the/every, each/which beautiful place)
Indefinite type article combinations: Ein schöner Platz, kein schöner Platz, mein schöner Platz,... (Ein/no/my beautiful place) Note that the possessives like mein/dein/sein/ihr/euer/unser behave like indefinite articles rather than an adjective.
no article: schöner Platz
The ending of the adjective depends on four things: 1. the (3) types of article preceding: definite, indefinite, none 2. the (4) cases: nominative, genetive, dative, akkusative 3. the (2) numbers: singular, plural 4. the (3) genders: masculine, feminine, neuter
While this amounts to 3 x 4 x 2 x 3 = 72 possible combinations, but don't worry too much. It is mostly just -e or -en.
Someone else has described this to make it much easier than learning 72 possibilities.
Reading it over, I should add that only one type of word gets the marking ending: article or adjective. Whenever there is more than one adjective, all will get the same ending.
Mein roter kleiner Knopf. My red small button. indefinite article mein, adjectives rot, klein
Der rote kleine Knopf. definite article der, adjectives rot, klein
Roter, kleiner Knopf. Small red button. no article, adjectives rot, klein