Apps open when not asking them to open

Hi, I was hoping someone can answer why this happens. When I type in a forum sometimes or something else i enter some text and all of a sudden the calculator will pop up even though i did not ask for that to happen.

Another example as I was typing in this thread, the start, all programs with docs, pics music..etc pops up. Why does this happen and how?

Is there a way to prevent it? Is this a shortcut issue where you type in a few combination of things and they just open on there own?

thx