A trademark search is a search of various types of databases and information related to existing names and trademarks for certain goods or services to determine whether a proposed trademark is available for use in connection with the goods or services to which it pertains.
Performing a trademark search is a crucial step before adopting and applying to register a trademark. A trademark search will alert you to potential legal problems on the horizon before it becomes too late. Individuals and companies who fail to perform a trademark search early on often come to regret it when they later find themselves embroiled in expensive legal disputes or needing to change their trademark both of which could have easily been avoided.
Once you have selected two or three trademarks that you like and are considering adopting, it makes sense to undertake a trademark search. If the search reveals that your trademark is not available, then move on to your second favorite mark, then the third, etc. If the search does not reveal any problematic marks, then you can commission a comprehensive trademark availability search to see if any other databases disclose any potential legal problems. You may also want to consult a trademark attorney early in the selection process to obtain general information about the relative strength of your proposed trademarks and whether they meet other criteria for registration.
You can yourself can do the trademark search. But, until and unless you are a trademark attorney, you are unlikely to know whether a disclosed trademark presents a legal problem. Accordingly, it is best to have a trademark attorney to do your search.