Learning how rto play an instroment on my own!

A sharp means that you raise a note up by a half-step. A half-step is the "space" between two adjacent keys on a piano, (regardless of color) or the space from one fret to the next on a fretted instrument like a guitar, for example. When I say "space", I really mean the change in pitch. A half-step corresponds to an increase in frequency of about 5.9463%. If you know the theme song to the movie Jaws, those two repeating notes at the beginning are a half-step apart.

A flat is the opposite of a sharp; it means that you lower a particular note by a half-step.

A C-sharp is the same pitch as a D-flat. A D-sharp is the same pitch as an E-flat. Etc.

A natural means that you do neither; you play the note without raising or lowering (on a piano, for example, any natural note will end up being a white key).

If you're wondering why there would be a symbol for a natural, it's because music is often written in keys that automatically have certain notes which are always played with a sharp or a flat. The natural symbol is to override that default. For example, if a piece of music is written in the key of G major, each musical staff in its sheet music would have a sharp symbol on the line corresponding to the note F. That notation implies that all F's within the music are to be played as F# (F-sharp, i.e. F raised by a half-step), unless specifically directed otherwise (which would be done with a "natural" symbol if the F# was supposed to be lowered by a half-step).

One more thing: Some natural notes are only separated by a half-step. E and F are one pair; B and C are the other. That's why, when you look at a piano, there are fewer black keys than white keys. The black keys are missing between each E-F and B-C pair of white keys. For those notes a sharp or flat still means the same thing - you raise or lower the pitch by a half-step. A B-sharp, for example, is the same note as a C-natural. A C-flat is the same note as a B-natural. The same goes for E and F.

Hopefully that makes sense for you.