Router Introducation

There is many types of router is provided with different Ethernet ports, Interface Card, Advanced Integration Module slot, console port, auxiliary port.
Here some of this is,

Router: 1841
The Cisco 1841 Integrated Services Router provides two fixed 10/100 (100BASE-TX) Ethernet ports, two integrated High-Speed WAN Interface Card (HWIC) slots that are compatible with WAN Interface Card (WI Cs) and Voice/WAN Interface Cards (Civics), and one internal Advanced Integration Module (AIM) slot.
Router: 2620XM
The Cisco 2620XM Multiservice Router provides a one-network module slot platform with one fixed 10/100 (100BASE-TX) Ethernet port, two integrated WAN Interface Card (WICK) slots, and one Advanced Integration Module (AIM) slot.
Router: 2621XM
The Cisco 2621XM Multiprocessor Router provides a one-network module slot platform with two fixed 10/100 (100BASE-TX) Ethernet ports, two integrated WAN Interface Card (WICK) slots, and one Advanced Integration Module (AIM) slot.
The 2621XM supports the same modules that the 2620XM supports.
Router: 2811
The Cisco 2811 Integrated Services Router provides one Enhanced Network-Module slot with two fixed 10/100 (100BASE-TX) Ethernet ports, four integrated High-Speed WAN Interface Card (WICK) slots that are compatible with WAN Interface Card (WICs), Voice Interface Cards (Vi Cs) and Voice/WAN Interface Cards (Civics), and dual Advanced Integration Module (AIM) slots
Router-PT
The Router-PT generic router provides ten slots, one console port, and one auxiliary port.