What are the differences of running on a treadmill verses outside?

I have been running on a treadmill for a long time and love it and feel great. The other day I ran in a park and today my legs are very sore like I have never run before in my life. Do I need to run outside more?

What are some easy tips on improving my running?

It has been a long time since I have actually just ran/jogged. Last night it was hard to keep pace. I am larger breasted too which adds to it. I did wear double bras over my tank.

But what can I do in simple things to gain endurance of running? What do runners usually eat?

Thanks for your help.