in this sentence for runnin dhcp server what is the minin of bold and coloride sentence?

Normally if you have a cable modem or DSL, you get your home PC's IP address dynamically assigned from your service provider. If you install a home cable/DSL router between your modem and home network, your PC will most likely get its IP address at boot time from the home router instead. You can choose to disable the DHCP server feature on your home
router and set up a Linux box as the DHCP server.

what is the mean of modem in this sentence?plz describes in detais as what is the meaning of the sentence?