if you mean the star rating, Muurta is correct, it's just rating how effective a spell it. keep in mind though you need to use some common sense, the ranking system isn't perfect. friends could rank it repeatedly, even the person who posted it, so it can't be ranked up or down without a lot of people voting. also, it could be ranked by a single person once, so if one person voted it 5 out of 5 [be it a working spell or not] the sell will appear as a top ranked spell in that section.
spells also have levels, not a lot, but a spell is typically 'high' or 'low' magic. 'low' magic is easier to cast with less change of backfiring, so many beginners start with them. [like candle magic] high magic takes more time, focus, ingredients, and risk of backfire. if someone doesn't know what they're doing tries casting one, it'll probably backfire and wind up hurting them in some way. [curses are normally high magic] you need to think well before casting any type of spell mind, because they're always a chance of it backfiring, some are easier/safer than others is all.