I was looking some routers and I noticed that in some of them there is a distinction between WAN and LAN ports? The WAN ports is to connect an access point and LAN ports to connect a switch or a PC?
Consumer grade routers generally have this distinction, although some enterprise SOHO routers also have this distinction. WAN stands for Wide Area Network and this is the network that connects your router to your service provider. The WAN port usually connects to a DSL modem, cable modem or fibre media converter. LAN stands for Local Area Network and this is the network that connects the devices within your home/business to the router. The LAN port or ports usually connect to PCs, printers etc. LAN ports can also connect to wireless APs to allow laptops, smartphones, tablets etc to connect to the LAN. The router then routes between the LAN and WAN network, applying NAT and firewall policy in the process.
A LAN is typically something completely within your own premises (your organization's campus, or building, or office suite, or your home), so it's something you build and own yourself, all the way down to the physical cabling. In contrast, a WAN is something that connects between geographically separated locations, so you generally have to lease access to lines or data transmission services from telecommunications carriers to create your WAN.
Because of the shorter distances needed for on-premises networks, and because of the focus on connecting PCs and servers, LANs tend to be built on Ethernet and other 802.3-family (and 802.11-family) physical layers and data links. 1000BASE-T, 1000BASE-SX, 1000BASE-LX, etc.
Because off-premises network links usually need to go longer distances and work over the telecommunication carriers' existing infrastructure, they tend to use physical and data-link standards that are more common in the telecom industry. Then again, for your convenience, telecom carriers usually hand off to you using an 802.3-family link, even if what they're using behind the scenes is, say, OC-3 and SONET/SDH.
Because of the technical hurdles associated with moving lots of data long distances reliably, WAN links tend to be lower bandwidth and higher latency than LAN links. Also, because you're usually paying a separate telecom carrier for the service, to keep costs down, most organizations try to limit (or at least not go crazy with) how much data they move over WAN links.
The differences between LANs and WANs tend to be at the physical and data-link layers. At the network layer (Layer 3 in the old-but-still-helpful-for-some-discussions OSI layering model), most people use IP (Internet Protocol) nowadays. Because it all uses IP, applications that use IP don't have to know what physical and data-link layers are in use, so anything you can do on a LAN you can potentially do on a WAN as well, if you have high enough bandwidth and low enough latency for whatever it is you're trying to do, and as long as you haven't blocked it at your firewall (or via the accidentally firewall-like properties of a NAT).
Typical home/small buisness routers are designed to connect a single local network LAN to a larger network (usually but not nessacerally the internet) usually with NAT (though NAT can be disabled.
The LAN ports connect to your local network (whether wired or wireless), the WAN port connects to your internet connection.