This is the study of tissues and their structure, tissue samples are taken in the form of biopsies, then fixed and stained with specific stain to visualise different parts of the tissue. For example, there are specific stains to visualise the nucleus, cytoplasm and intermediate filaments.
Studying histology will give you an appreciation for number of steps involved in diagnosing a patient using a biopsy sample. You will learn about the different biopsy techniques I have put a link to a useful website for this in the reading list. Then you will learn about the fixation of tissues to prepare it for staining and how to do it without damaging the tissue (creating artifacts)
You will be taught how to differentiate between different types of pathologies and be able to stage cancers from tissue samples under a microscope.
The most difficult part of studying histology is the recognition of tissue types down the microscope. This is something which can only be learn by actively applying yourself to learning how to spot the different types.
This subject is very practical and normally involves lots of lab work. Using real tissue samples and normally going though the entire process from fixation to staining to diagnosis.