Working at Google Help?

[unknown]

Okay it say on the Google jobs site under the requirments this:

BS or MS in Computer Science or equivalent (PhD a plus).
Several years of software development experience.
Extensive experience programming in C++ and/or Java.
Enthusiasm for solving interesting problems.
Experience with Unix/Linux or Windows environments, C++ development, distributed systems, machine learning, information retrieval, network programming and/or developing large software systems a plus.

So i have a couple questions about some of these.

1)What is a BS or an MS and how long does it take ?
2)It says several years of software development experience. How can you get these years of experience? Like what other kind of job?