Do different strains of Cannabis really effect you in different ways and if so how?

There are three different species of the Cannabis Sativa plant.

Cannabis Sativa Sativa - Simply put: it gives you an uplifting high.

Cannabis Sativa Indica - Again, simplified, it makes you stoned (i.e that "couchlock" effect).

Cannabis Sativa Ruderalis - Contains so little THC that it is never used in marijuana strains.

Now, you can argue that the way you grow the plants (if you use real soil, and if so the quality of it, fertilizers, and the general proper conditions for growing etc) affects to a certain degree how the effect will be, but generally what growers do is to make strains based on a Sativa/Indica mix. A rule of thumb is that the more Cannabis Sativa Sativa that is in your strain, the more of that uplifting high you will get, and the same with Cannabis Sativa Indica only with the "couchlock" effect.