The red cell block on a blood count is longer than it needs to be, because it describes the same cells from several angles. Three are measured, and the rest are arithmetic.
What a blood count covers
MedlinePlus lists the components directly: "A CBC measures: Red blood cells, White blood cells, Platelets, Hemoglobin, Hematocrit, Mean corpuscular volume (MCV)."
The three red cell measurements
RBC count — how many red cells are in a volume of blood. MedlinePlus describes what they do: "Red blood cells, which carry oxygen from your lungs to the rest of your body."
Haemoglobin — "an iron-rich protein in red blood cells that carries oxygen from your lungs to the rest of your body." This measures the protein itself, not the cells carrying it.
Haematocrit — "the amount of whole blood that is made up of red blood cells." A proportion, so it is usually printed as a percentage.
These three answer different questions: how many cells, how much oxygen-carrying protein, and how much of the blood's volume the cells occupy.
The indices, which are calculated
MCV — mean corpuscular volume, "the average size of your red blood cells." Derived from haematocrit and the red cell count.
MCH — mean corpuscular haemoglobin: the average amount of haemoglobin per cell, from haemoglobin and the count.
MCHC — mean corpuscular haemoglobin concentration: haemoglobin relative to haematocrit, so the concentration within the cells rather than per cell.
RDW — red cell distribution width, describing how much cell size varies rather than what the average is.
Each of these is computed from the measured values above, which is why they move when their inputs move. A report may print them without marking them as derived.
Platelets, in the same block
MedlinePlus: "Platelets, which stop bleeding by helping your blood to clot." MPV — mean platelet volume — is their size analogue, the same idea as MCV applied to platelets.
Reading the block
Because the indices are averages over the measured values, they carry the same limitation as any average: two very different populations of cells can produce the same MCV. RDW is the column that describes that spread, which is why it appears alongside rather than instead.
None of these say what a result means for you. MedlinePlus's general caution applies here as much as anywhere: a result outside the range "may or may not be a sign of a health problem", and the reference interval to use is the one printed on your own report.