Each Cricut mat was created for different materials and purposes.  This means that each of the mats has a different level of stickiness. 
These range from a strong adhesive for heavy projects to light adhesive to light weight projects.

All of these mats come in different sizes, the most popular ones being 12x12, or 12x24. 

I recommend getting your Cricut mats from Joann's when they are 30% off. Those are the best prices I have found, by far.

BLUE CUTTING MATS - Used for lightweight projects

• Construction Paper
• Copy Paper
• Lightweight cardstock
• Vellum 
• Vinyl
• Washi Tape Sheets
• Wrapping Paper

PINK CUTTING MATS - Used for fabric projects

• Bonded Fabrics
• Crepe Paper
• Fabrics
• Felt

GREEN CUTTING MATS - Used most often for general projects

• Cardstock
• Embossed cardstock or textured paper
• Iron-on Vinyl
• Patterned paper
• Vinyl

PURPLE CUTTING MATS - Used for Heavy Weight Projects

• Balsa Wood or Basswood
• Chipboard
• Corrugated Cardboard
• Fabric with stiffener
• Glitter cardstock
• Leather or Faux Leather
• Magnet material
• Poster board
• Thick cardstock