An integer is a whole number, e.g. 1, 42, 256; and can range from -2 billion to +2 billion (or so). They are represented in AppGameKit by using a word. e.g. score = 0;
A real number (or float) is one which has decimal places. e.g. 0.01, 3.141, 256.7; These are represented in AppGameKit by using a word with a # at the end. e.g. pi# = 3.141, playerx#=55.7;
A string is a variable which holds text rather than numbers (whole or otherwise), e.g. Hello, fish, super-duper; These are represented in AppGameKit by using a word with a $ at the end. e.g playername$="Dave";
I hope that helps.