As a beginner you might want to ignore those terms completely, and simply use the web interface in a web-browser, e.g. by using the SEED viewer or myRAST (which is a windows and mac software). SOAP and API are terms used for programmatic interfaces and web-services (possibly their most important function is to scare off beginners ;) ). They are not even always installable software in the strict sense, but a set of conventions and definitions. I agree that these things are important, but only so for programmers who want to connect their applications to other programs, or in case you want to run huge batch queries. Therefore, unless you know you need to make a computer program connecting to SEED and Rast, you do not install any additional software on your computer. Certainly, which tools you need depends on what you want to do, and maybe RAST is not even the best tool for your purpose, but to understand your task better, you would have to be more specific in your question. See e.g. this review article.