Only, the problem is, these four things are not exactly the same in everyone heads. Let's see why shall we?
A headline is a line appearing at the very top of an advertisement, newspaper, article or page. It's something to catch the eye of your potential customer or client and hook them in.
A strapline is a line that sums up the brand or company in a line, representing the culture, identity and personality of the brand.
A tagline is just another word for a strapline.
A slogan is a phrase that is traditionally used to enter competitions but can also be used as slang by clients to ask for a catchy headline or strapline.
Why does this difference matter? Well. A headline is used to summarise an article, blog, newspaper page, etc and to draw in a reader meaning it has a single focus on the content beneath it. It is by its very nature, designed to draw the reader down into the content beneath.
A strapline, however, is a brand building tool which becomes a recognisable long-term asset for the business or company. They tend to get copyrighted and protected as well. Such wonderful sayings as 'You can do it when you B&Q it' and 'Have a break, have a KitKat' are easily recognisable as the brands they represent.
Where does that leave slogans? Slogans used to be for competition entries. Remember those days where you would submit a describe our product in '10 words or less' competition entry to a company and be in the running for a prize? Those were the days. Somehow, slogans have got mixed up in all the marketing terminology.
So, for a TLDR:
Headline - goes at the top of the page/ad/newspaper
Strapline/Tagline - goes near the logo/branding
Slogan - Competitions! Or maybe a t-shirt phrase.
Simple. Are you looking for a strapline, tagline or headline? Consider our copywriting services and see what we can do for you.