One of the primary factors the USPTO considers in determining whether to allow a mark for registration is whether there exists a likelihood of confusion between the proposed trademark and a registered or pending trademark for the goods or services covered in the application. The USPTO considers: (1) how similar the marks are, and (2) the commercial relationship between the goods and/or services identified by the marks. The marks do not have to be identical to be confusing.
There could be similarities in appearance, sound, meaning or commercial impression to support a finding of likelihood of confusion.