.co (abbreviation of commercial) is a second-level domain analogous to .com (in a strictly second-level sense) in a number of countries, in which registrants (usually companies) may register second-level domains of the form .co.xx, where xx is the ccTLD (e.g. co.in, for India).
Locations using this include India (.in), Indonesia (.id), Israel (.il), the United Kingdom (.uk), South Africa (.za), New Zealand (.nz), Japan (.jp), South Korea (.kr) and Cook Islands (.ck). The code is not permitted on any countries in which the .com code exists, suggesting a correlation between the two.
The Colombian registry .co is capitalizing on this usage, offering commercial institutions and corporations Internet domains ending in .co.[1]