New knitters and crocheters usually start with projects that are small, flat, and rectangular, like dishcloths and winter scarves. Usually these projects completely ignore the issue of gauge, as it just doesn't matter. You knit or crochet until it's the size you want, and you're done. And that's fine, as long as you never want to make anything else.
Yarnologue posted an excellent explanation of knitting gauge, why it matters, and how to adjust to get the correct gauge. This information applies to crochet as well.
There, now that you understand gauge, go forth and drown your parents in socks, gloves, and hats. Heap piles of plushies upon your nieces and nephews. Stop your sister's shivering with shawls.
Just don't knit a sweater for your boyfriend.