The MCP3008 is a low cost 8-channel 10-bit analog to digital converter. The precision of this ADC is similar to that of an Arduino Uno, and with 8 channels you can read quite a few analog signals from the Pi. This chip is a great option if you just need to read simple analog signals, like from a temperature or light sensor. If you need more precision or features, check out the ADS1x115 series on the next page.
Before you use the MCP3008 it will help to skim this older Raspberry Pi MCP3008 guide for more information about using it with the Raspberry Pi. However don’t use the code from the older guide as it’s deprecated. This guide will show you an easier way to install and use new Python code to talk to the MCP3008 ADC.
The MCP3008 datasheet is also an important resource to skim and have handy.