zhe4 means "this". "ge" is a classifier, it has nothing to do with the meaning of "zhe4". Between a noun and a demonstrative pronoun it´s necessary to put a classifier, for example: 这个人 zhe4 ge4 ren2= this person. other nouns will require different classifiers, for example, zhe ben shu (this book). You have to learn the right classifier for each noun.

Firstly, 个 does not have a meaning. It's one of the many measure words in Chinese that are placed before nouns. The same way we say "a *loaf* of bread" and "a *pair* of shoes" not 'a pair of bread' and 'a loaf of shoes." 个 is the most commonly used measure word in Mandarin and is used for people and most objects. 这个can be translated as "this[thing]" i.e. 这个书包-this book bag, 这个人- this person. In English "this one" can openly refer to anything in the world. A cat, a cake, a television set, a computer or a house or even a magazine. In Mandarin however, measure words let us know what is being talked about i.e 辆 refers to vehicles, so if someone says "这辆“ they are most likely referring to a car. Or if they say: 那条 they are referring to something long and/or skinny i.e. 这条狗(this dog) or 这条连衣裙(this dress)，五条金鱼(Five goldfish). The measure word you use is very important: 一个蛋糕 means "one cake" while 一片蛋糕 means "a slice/piece of cake" 这 means "this".那 means "that".

As edu explained above it is the zhe that refers to this not the ge. Incidently if you say 这些 zhe4 xie1 那些 na4 xie1 (些 meaning several) it turns into the plural "these" and "those". So you can say 这些女人 zhe4 xie1 nv4 ren2 - these women.

actually...zhe4. 这（zhe4）means this...or something you point to. 个(ge4) means "the one"... so...这个=this one

zhe4 ge4= this,na4 ge4=that