On day hikes I talk and think about regular life (talking if there's someone else there.)
On a backpack trip I find it takes 2-3 days before home/work life is gone and trail life has taken over. Then I think a lot less, talk a lot less and my thoughts are all about what's happening in the moment on the trail.
On a long-distance hike my thoughts go a million miles an hour. So much happens on the trail. Every moment is jam packed with stuff happening. So much to see and think about.
I think about food, about writing stuff down in my journal about every little detail I see of the animals, rocks, plants, scenery. I think about about family at home. Music runs through my head and sometimes it gets stuck there, sometimes words get stuck in my head, too.
I think about what's coming up, how I'm going to split the days up to the next resupply, how many miles to the next water, food and more food, what I'm going to eat next on the trail, what I'm going to eat when I get to town. Sometimes I think fondly about taking a shower.
Oddly, even though my thoughts go a million miles an hour and trail life is jam packed with stuff happening, I feel slowed down, calm, like I could go weeks without ever saying another word. But when I meet another hiker, we both talk a million miles an hour about everybody we've met, great experiences we've had, trail intel and food.
When I get to town I feel assaulted by people who talk fast about things I no longer understand and sometimes I have a hard time making sense of what they are saying. The trail I understand now, not regular life. I love it when it gets like that.