SAMP asked for just a password that could be adjusted in the server's configuration files, but it worked in a way that blocked client connection request before even connecting to the server. This functionality was useful for private servers, beta test servers etc. It'll be even more useful for RageMP which has client file downloads, these downloads should not even happen if the login is incorrect and hence protect people from downloading/stealing files.
Here's a screenshot that I lifted from Google. The first box is for the server password and the second is the RCON password. Actual game account login happened after succesfuly connecting.
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Where's the download for 1.1 btw?