Ethernet UTP (Unshielded Twisted Pair) cable comes in various types -

CAT-5 - 4pr, Solid or stranded 24AWG, 100MHz
CAT-5e - 4pr, Solid or stranded 24AWG, 350MHz
CAT-6 - 4pr, Solid or stranded 24AWG, 550MHz

CAT5e is the newest version of CAT5 cables, formally called ANSI/TIA/EIA568A-5 or simply Category 5e. CAT-5e is completely backward compatible with current Catagory-5 equipment, and Category 5e will operate at up to 350MHZ, instead of the 100MHZ of standard CAT 5 cables. The enhanced electrical performance of CAT 5e ensures that the cable will support applications that require additional bandwidth.

CAT6 - The highest performance unshielded twisted pair (UTP) cable available today. The construction isolates the pairs throughout the length of cable, while providing an installer-friendly cable.The CAT6 construction isolates the cable pairs and enhances the pair-to-pair balance for superior crosstalk and LCL and LCTL performance. Compact cable design that meets the diameter requirements specified in TIA/EIA-568-A, providing flexibility and ease of installation.Tested to 550 MHz - With verified stability, 37% increase in power due to lower attenuation characteristics at 100 MHz and greater that 50% at 250 MHz and beyond More than 12% Crosstalk Improvement vs. Category 6. More than 33% increase in ACR headroom at 100 MHz and greater than 300% increase at 250 MHz and beyond. ....mmmmmhh, Amazing stuff!

Solid or Stranded?

Solid Cable is recommended for all horizontal runs, between wiring closets, and for lengths over 25 feet. Maximum recommended length is 100 meters (328 feet). It should not be flexed.
Stranded Cable is built to withstand the repeated flexing, common in PC to wallplate applications, without damage to inner conductors. Because of higher attenuation it is recommended for short runs of 25 feet or less.

Plenum Rated?

Due to fire regulations, plenum rated cable is generally required in all air returns, dropped ceilings and public buildings.