You're using a Netgear DSL modem with an integrated router. He means to leave it off for a while then power it back on (about a 15 minute cooldown time should work.)
Check with reviews on your ISP to see if other people get it too. Could be your ISP throttling (dealt with this before, they never say it's on their end.)
Are you using a 10Mb, 100Mb, or 1000Mb (gigabit) connection to the router?