Xx or Xxx when chatting usually represents a kiss. It is a common way to end a chat, text message or email, and is often found in birthday cards where somebody signs their name.
xxx is also sometimes written as "xoxo", which means hugs and kisses.
The practice of signing off correspondence this way dates as far back as the middle ages where a Christian cross †
was placed on documents as an indication of sincerity, and then the author would place an 'x' on top of this to show their allegiance to this.
"In Christ's name, this is true".
In modern times although xxx's represent kisses, there is nothing romantic in using this sign off. It is common for people to use it among friends, acquaintances and even people they are contacting for the first time, and is really just a sign of friendliness, like the use of " :) " representing a smiley face.