A pride flag is any flag that represents a part of the LGBT community. The word pride used here is talking about gay pride. The terms LGBT flag and queer flag are sometimes used instead of pride flag.[1]
The rainbow flag is the most widely used LGBT flag and LGBT symbol in general. There are versions of the rainbow flag that are used to focus on specific groups in the community. There are also some pride flags that are not just related to LGBT, such as the polyamory flag.