What are the three main configuration modes in Cisco IOS and their prompts?

Question

Accepted Answer

Global config (config)#, Line config (config-line)#, and Interface config (config-if)# — the line and interface modes are reached from global config.

Mode
Purpose
Prompt

Global Configuration
Access configuration options on the device
Switch(config)#

Line Configuration
Configure console, SSH, Telnet, or AUX access
Switch(config-line)#

Interface Configuration
Configure a switch port or router interface
Switch(config-if)#

All subconfiguration modes are accessed from global configuration mode.
Go deeper:

Cisco IOS — configuration sub-modes (Wikipedia) — how global config branches into line, interface and other sub-modes, each with its own prompt.

Mode	Purpose	Prompt
Global Configuration	Access configuration options on the device	`Switch(config)#`
Line Configuration	Configure console, SSH, Telnet, or AUX access	`Switch(config-line)#`
Interface Configuration	Configure a switch port or router interface	`Switch(config-if)#`