In caffe project, there are both .proto file and .prototxt file.
From Google Protocol Buffer documentation, .proto file defines the protocol, so what about the .prototxt, is it defined in Google Protocol Buffer, what's the different between them?
The .proto file is used to describe the structure (the 'protocol') of the data to be serialized. The protobuf compiler can turn this file into python/or C++/or Java code to serialize and deserialize data with that structure
For the .prototxt file. Looking at the documentation here, we can see that, there are two different formats for serialized data (textual or binary). The text format is human-readable and modifiable (and the corresponding files usually have the extension .prototxt), but it takes up a lot more space than the binary format.
来源：https://stackoverflow.com/questions/44125534/whats-the-different-between-proto-and-prototxt-file