What does it mean when people type "#" in twitter?

[Khalid]

Some people type "#" then a word, why is that and what does it mean?
Thanks
What happens if i protect my tweets? do they also show?

[Roubina]

When you type # before any word without space then it mean your specify your keyword by which any body and you search with this keyword then you get your all tweets those which specify by that particular keyword in search result. It" # " specify only your keyword.

[kkkkk]

i don't know about "#" but if u protect your tweets no one can retweet them