Hi @elina2410,
Welcome to the :qiime2: forum!
Great question - feature count can refer to the total number of features observed, or the number of times a specific feature was observed (within a given sample, etc). I would advise against referring to ASVs and features interchangeably however - @Nicholas_Bokulich has a very concise description of the difference between ASVs and features, which you can find here (with further explanation on the general definition of a feature here).
A chimeric read (or split read) means that multiple subsections of a given read align to multiple distinct portions of the genome with little or no overlap. Non-chimeric reads refer to any read that aligns with a continuous portion of the genome (i.e. a 'real' segment of DNA that exists in the wild).
Hope this helps! Cheers 