What is a Hashtag?
Hashtags are popular on social media especially on Facebook and Twitter. It is usually a single word or phrase used to amplify the meaning, theme or topic being discussed in a post. It should not have spaces between words and other special characters like punctuation mark or symbols cannot be used. Although you can use numbers, you should have at least one letter.
The # (pound/number sign) Symbol
The hash, pound or number sign is being used to highlight a keyword, In other countries in Europe this is called a hash sign.
The hash is normally written at the end of the sentence. Read more here: http://www.drivetrafficmedia.com/hashtags-on-social-media/