What is the plantar fascia? What is fascia? Why do you care?
I'm starting with question 3: You care because it hurts if you have problems with it.
Now question 2: fascia is the stuff that holds your muscles apart from one another. It's the sheath that encloses a muscle, tendon, or other organ. It's our body's way of separating it's inside parts. You see fascia when you eat chicken. It's the slimy film that separates the muscles. Nice. Anyway, we all have it and when it adheres to the structure that it is surrounding we get what is known as adhesions.
And that doesn't feel so nice.
Now for question #1: What is the plantar fascia?
The plantar fascia, which is really more like a tendon than a thin sheath, is a broad band that spans the space between the heel bone and the toe bones. (calcaneus, and proximal phalanges). When it becomes irritated, the condition is known as plantar fasciitis. And there are some things you can do to help it. Rest is a start but there's more! In addition to easing up on running and jumping, here are 3 other ideas to help.
1. Freeze Dixie cups full of water and massage the area. This is a little messy, so you'll want a towel around, but it's ice is nice.
2. Use a lacrosse, tennis, or other sports ball on the bottom of your foot to encourage the breaking up of the aforementioned adhesions.
3. Roll your gastrocnemius, soleus, and plantaris muscles. That is, your calves. See the pictures. These guys are attached to your heel bone and when tight will pull on other structures. The best tool I have found for this is called a Rolflex, what used to be called a Rubbit. It's on Amazon and you need this. Oh, and check out the videos to see just how good it feels. :)