> it's a little tsu (tsu being the sound if it is not little - observe ツ compared to ッ), essentially a glotteral stop (or if you want to get really technical, it is a geminate consonant)
It has no meaning by itself.
It is used to indicate a slight pause in between two sounds in Japanese. For instance, if you say the word 'rock' (or how I say it anyway) you will find a pause between 'ro' and 'ck' (if you say it without the pause, it will sound more like 'rawk'). You probably wont hear it though, as in English we don't really need to use it to make a distinction between words that sound simil…