Babies will learn to sit up first before they learn to crawl and then after crawling the baby will usually begin pulling themselves up on things such as a couch, coffee table etc.
Most babies begin sitting up independently as early as 4 months of age and then around 7 to 9 months of age the baby will begin to crawl.
Your baby will begin pulling themselves up on things around 9 to 12 months of age and then after 12 months of age they begin walking but may need some help.
For awhile when your baby starts standing up and trying to walk they will fall on their butt for awhile and may need some help to walk for awhile.
Once your baby reaches 15 months of age they should be able to walk without assistance and will be taking off on you.
Some babies skip crawling and go directly to pulling themselves up and try to walk.
Every baby is different and they have milestones at different ages.