What are you afraid of? Spiders? Heights? Maybe mice? I'm afraid of moths (eugh! Big, hairy, horrible things...) I'm also afraid of getting trapped underground.
So, afraid of + noun / gerund (-ing) = a fear
What are you afraid of?
Ok so far? Right, so what about afraid to? How about this: "I'm afraid to talk to my boss today, because he is in a very bad mood". This doesn't mean that I am always afraid of my boss, it's not a fear (see above). If it was, I would say "I'm afraid of talking to my boss". See the difference? No, in this case I'm afraid to talk to my boss today, at this moment, temporarily.
Other examples could be:
"I'm afraid to go outside because of the storm." Remember Hurricaine Irma in Florida?
"I'm afraid to look in the box because I think there is a spider in there." And they move so fast!
Are you afraid to do anything right now? Why?
Remember, only use afraid to if you are genuinely nervous or scared about the action; otherwise it doesn't work. "I'm afraid to try the spaghetti because I might not like it." Really? You're afraid to try it?
So, now we move onto afraid. If I say "I'm afraid", what do I mean? On its own, it means I am scared, right? Yes it does. Imagine I hate flying, and I'm siting on a plane. As the plane accelerates down the runway, faster and faster, I turn to my husband and I say "I'm afraid". Context is everything. However, what about this: "That product is out of stock, I'm afraid." What? Why are you afraid? That doesn't make sense! In this case, I'm afraid is an apology. It's the same as saying "I'm sorry, but that product is out of stock." It's only ever used in a negative context. Here are a few more examples:
"I can't help you, I'm afraid."
"I'm afraid the flight is delayed." (It can be used at the beginning or the end of the sentence.)
"I'm afraid we are fully booked today. Can you come tomorrow?"
"The line is busy, I'm afraid. Can I take a message?"
What other examples can you think of, from your own workplace?