You need to hyphenate descriptive words. What does that mean? Let me explain:

I wish I had noise-canceling headphones to drown out all the sales guys at work.

A hyphen is used here (but is not absolutely necessary) because “noise” and “canceling” are acting as a compound modifier, modifying “headphones.” These examples are detailed fully on Grammar Girl.

Hyphens are a “look-it-up” punctuation mark. Though hyphens have several uses, we’re going to focus on how to use hyphens with compound adjectives. Compound adjectives are two or more words that together make an adjective. When they come directly before a noun, they’re known as compound modifiers and usually have a hyphen, like “noise-canceling headphones.” Here are a few more examples:

They had a long-term relationship.

The fire-proof vest proved to be a great life saver.

If the adjectives come after the noun, then they don’t need a hyphen. For example

Their relationship was long term.

Santa’s new vest is fire proof.

These terms need hyphenation in your brochures, web copy and emails because they are always used to describe something:

In-depth

Best-in-class

Buy-in

End-to-End supply chain

Up-to-date

On-site

Top-of-the-line

Hands-on

Step-by-step

Real-time

These terms are one word and not hyphenated:

Firsthand

Unpredictable

Beforehand

Unforeseen

Uninterrupted

Inconsistency

Derail