1. Any person can edit it (no qualification, no designation, nothing required).
2. Whenever some changes in any article is made by anyone, the authority of wikipedia checks if it is right then it is approved, but if its wrong, its deleted.
3. Now for example if someone writes that Obama is president of India then sure that is wrong one and will be deleted. But if someone writes that Lady Gaga was toper in school, as it might seem alright and wikipedia authority will leave it, but it is likely to be wrong.
4. This has even been proven and there are many case such as a the one in which a journalist used some data of wikipedia which was later confirmed to be wrong. This is the entire story about it. Infact there has been so many case for which wikipedia reliability can be qustioned. Even there had been errors which lasted for more than an year.
5. Options other than wikipedia are encyclopedia, britannica, infoplease, citizendium, columbia, conservapedia, doosan, everything2, faqs, gnu , open-site, newworldencyclopedia, talktalk and many more.
6. Even the wikipedia says that itself. Check out “We do not expect you to trust us” column in Wikipedia:Ten things you may not know about Wikipedia.