Do you know that oldie but goodie by Little Eva, "The Loco-Motion"? I'm guessing that could your little one's current theme song. Creeping around (moving around while the belly still touches the ground) then to scooting (moving around with one leg moving) to full-blown crawling (on hands and knees). Triumphantly getting from A to B!
Like everything else, for some this is happening now, while others may not locomote much for another few months. (Some normal babies never crawl at all but go from sitting to walking, thereby avoiding the middle man!) A few of yours may even be pulling to stand and taking a few hesitant, independent steps And look at for that "neat pincer" grasp, which will scoop up and put into the mouth the smallest visible objects known to man.
Your Baby's Language
Your baby's simple babbling now has probably morphed into complex "jargoning." It is complicated and sounds like real sentences, except in Martian, not English. (In my paranoid days, I decided all 10-month-olds were speaking their own language which they alone could understand and we adults couldn't. They are really saying things to each other like "Don't let the giants know you can talk, so they will think you are more helpless and do more for you then!")
Likely your baby is in the throes of stranger and separation anxiety (which we discussed in detail at 7 months). What this means is that, as in most developmental stages, human relationships are by far the most important for establishing emotional bonds and for learning about the world.
Your Baby's Thinking
Your baby's sense of object permanence is much better and she knows things continue to exist outside of her perception of them. Additionally, your baby is learning about what causes things to happen. Previously, things happened magically, but now she is learning it is pulling a switch that causes the room to be flooded with light or it is the turning of a switch on the wind-up toy that actually causes it to move. This is an exciting time for your baby, who is making great intellectual leaps!