A level qualifications are what UK students take between age 16 and 18 and are the the requirements for getting into university.
In US terms, they are approximately equivalent to AP classes in high school or the first year or so of US college.
So, if you have a bachelors degree, this is equivalent to a UK bachelors degree, which is 3 years ahead of (more advanced) than A levels.
A college degree with a 2.8 GPA is basically equivalent to a 2:2 (lower second class) bachelors degree in the UK.
In another format, UK qualifications are also measured in terms of the NQF scale (National Qualifications Framework). A college degree (bachelors) is equivalent to level 6 on the NQF scale, while A levels are only level 3.