Stupid question: What is SP3?

I use VB6 in Visual Studio 6.0 environment on a Windows 98 Second Edition system. I thought this identified my environment.

I see others referring to VB6 SP3. What is "SP3"?

I expect to feel stupid when I get the answer. I somehow think I should know the answer already.

My pet peeve is with those who post using a subject like "I need help", "Urgent problem", "I am going crazy", et cetera. I never look at a post that does not at least hint about the subject of the post.

SP3 would be Service Pack 3