Why do we have blessings (blessing of healing/comfort) when we have prayer?

I don’t mean to make it sound like I’m downplaying either one of them, prayer or blessings. But I have been wandering it lately.

What makes a blessing different than prayer as far as asking for help and blessings?

I think my question really is why do we we need to invoke the power of the priesthood for certain things?

For example, if someone is sick. Normally a husband, ministering brethren, bishop…etc would give a blessing of healing. Why is the blessing done instead of saying a simple prayer?

I don’t mean to question anything, it’s a genuine question that I was thinking about today. Are there any scriptures or anything I can read that relate to this?