What does the # sign mean in front of senctences?

[Fleur]

I see the # sign everywhere in front of senteces. I don't want to know the origin of it, but what it means for the past year when it's in frnt of sentences, not numbers. Thnx

[Chris]

The # is a hashtag, it's used on social media sites to group together all the posts relevant to that topic.
For ex. #LazyDay: Everyone who posted a status with hashtag "#lazyday" will be grouped together.

Lisa: Looks like another #lazyday
Dave: Literally did nothing today #lazyday
... ect.

[Natalie]

It's a hash tag, its what people use on social networking sites to tag their posts and sometimes people just use it for the humor of it

[Mista Soulo]

It's a "hashtag" they're used as highlight words basically... sometimes they summarize a post... it's like a "tag" you know? It highlights the main ideas of the post, so it helps people searching for what they wanna read or talk about.

It's like YouTube you "tag" your videos with relevant words to help people find your video.