"It's" always means "it is."

"It's," unlike pretty much all other words with an apostrophe and an "s", does not ever indicate a possessive.

"Its" is the possessive, strangely enough.

"It's a good program.": The same as "It is a good program."

"It's features are impressive.": The same as "It is features are impressive," which is wrong.

"Its features are impressive.": Correct!

When I took a typing classs (not a keyboarding class, and yes, I know that dates me) I was taught that words had one space between them and sentences had two spaces in between them. Therefore, my thumbs, whose only job was to hit the space bar, learned that when a period was the last key typed, they had to hit the space bar twice instead of only once. They were good at this and were quite proud of their skill.

Now the rules have changed. The convention, especially for�material to be read on a screen, is that sentences have only one space between them. My thumbs have been rebelling. When I type, they want to put TWO spaces after a period. When I am typing something formal, in addition to checking my spelling and grammar, I also need to�check how many spaces are between each sentence.

Luckily, my thumbs are starting to adjust, and I am finding fewer and fewer double spaces between sentences. Thumbs can learn new tricks.