Search engines send out "spiders" throughout the web to look at websites and report back to them about what they found. Spiders are just automated programs without the ability to think or problem-solve. Your site needs to make it as easy as possible for these spiders so there is no mistake about what your website sells.
If you have an online toystore, you need to have the word "toys" mentioned somewhere in the text of your homepage, preferably several times. Then, when the spider looks at your website, it can say "Aha! This website sells toys!" If you want to really give the spider some good reading material, your homepage should not only use the word "toys," it should also mention what kind of toys you sell. For instance, a good opening paragraph in your homepage might be,
"Toys-N-Things toystore has a wide variety of teddy bears, action figures, dolls, teasets, model trains and just about any other toy your children might desire."
This gives several keywords to the spider: Toys-N-Things, toystore, teddy bears, action figures, dolls, teasets, model trains, toy, children. The spider will know to tell the search engine to list your site under those keywords.