These are results from a urinalysis. Epithelial cells are cells that line the urinary and genital tract, and are very common in urine, as they slough off during urination. They are usually squamous cells, though large numbers of something called "renal tubular" or "transitional" epithelial cells can indicate some kind of urinary or kidney problem.
Normal urine is sterile, so the presence of any bacteria in the urine is due to infection or contamination of the sample. Occassionally, some amount of bacteria is present in urine in small numbers, and is often bacteria that is washed into the sample from the vagina or urethral opening. If your urine was collected from a catheter, the presense of bacteria would be more indicative of an abnormal sample (infection). Any bacteria found in the urine should be cultured further.
WBC stands for "white blood cells" that are found in urine. High amounts of these in the urine probably indicate a urinary infection (more than 5/hpf). Leukocyte esterase tests are also done on urine samples. A positive result also indicates the presense of white blood cells (WBCs). An abnormal number of WBCs can be indiciative of several conditions, usually a urinary tract infection, but also renal stones or disease. Since you do have a significant number of white blood cells and a positive esterase test, you need to be evaluated further for your pyuria.
I hope this helps!