TV Squad will be having extensive coverage of this week's network "upfronts," and I thought I'd take this spot to explain exactly what an upfront is. Basically it's the week when each network reveals its fall lineup. What new shows are coming on, and what old shows are being canceled. Each day this week we'll have the rundown as each network unveils their lineup. Here's the upfront schedule:

• Today: NBC
• Tuesday: ABC and WB
• Wednesday: CBS
• Thursday: Fox and UPN

Keep checking back throughout the week for breaking news...