Adult Sunday School
Is There Such a Thing as Adult Sunday School?
While adult Sunday School is rarely called by this name, there is indeed Christian education for adults. The forms it takes depends on the denomination in question. It also may not literally be on Sunday when it is limited to grown-ups.
Almost all (if not all) churches have Bible study, which is the usual form of Sunday School for adults. In it, specific passages of the Bible are chosen for further investigation. These can be gone into in great detail – far more detail than would be given in Sunday School for kids. This is partly because adults aren't very willing to just memorize things uncritically, and partly because grown-ups can usually understand more details than young children.
In some churches, there is a more direct equivalent to Sunday School. This is a catechism class. Not all denominations have this class, but some known to do it are Catholicism and Episcopalianism. Almost all denominations do have a catechism, whether or not they run classes to teach it in a formal way.
Of course, churches all offer plenty of services besides religious education classes of various kinds. In fact, the most popular offering is literally called the "service." This is a worship session that is run on a set schedule, with the main offering typically taking place on Sunday morning. Large churches usually have two or three Sunday services each week, while smaller ones will have one Sunday morning service. When there is only one service, it is typically scheduled for mid- to late morning. If there are more, one will almost always be at the crack of dawn and the other about two hours later. An evening service may also be offered.
It is also typical for there to be a midweek service of some sort. Often, this isn't as long or involved as the one(s) on Sunday. Instead, it will focus more on prayer, and have a shorter sermon. This is sometimes called the evening service, though it may have a different name if there is also a Sunday evening service offered.
What happens at a Sunday morning service varies by denomination. Some churches have a very formal program, which those who have attended for a long time will have memorized. For example, there may be a hymn sung, then a Bible reading, then a sermon, then another hymn or two, another Bible reading, and finally, a parting blessing. Each church of this type is a bit different from each other, so it's always easy to spot a newcomer.
Other, less formal, churches aren't this predictable. There may be many hymns, or even popular music, played before the service leader gives his or her sermon. However, there will always be a sermon, no matter what kind of church it is. This gives the leader a chance to impart Biblical knowledge and spiritual or life guidance to the congregation.
An evening service is less predictable, with plenty of variation between churches. However, it is common for there to be a sermon and at least some music. Often, it will be shorter than the morning service, but this isn't always the case. If you're checking out a midweek service, it can be a good idea to ask the usher or similar person about the length if you have another place to be later in the evening. This will ensure that you don't have to dash out before the service is done in order to make your next appointment.