How should I read these abbreviations on the Airbus 320 MCDU?
These are RNAV procedures as defined in ARINC 424 used for database coding. They define paths which an aircraft must follow during RNAV departures and approaches. Every standard departure and approach can be divided into distinct sections. Each possible path starts at a point and ends at a termination point. The file format is standardized so that each and every FMS system can read the same file format. You can get an overview at this link.
This document requires pilots to be trained in and familiar with the paths and terminators used in RNAV departure and arrival procedures.

Understanding this terminology gives the pilot a vocabulary and a framework to better understand how an RNAV computer navigates.

RNAV departure and arrival procedures are constructed using legs or segments defined by a path and a terminator.

The path is how you get the, i.e. heading or course
The terminator is the event that causes the start of the next leg, or the end of the procedure.

There are 23 path terminators combinations defined in ARINC 424

13 are used for RNV departure and approach procedures
Each procedure has a two-letter code.

Example:
RNAV procedures start at an Initial Fix (IF) which can be a fly-by or fly-over waypoint, followed by:
Track to a Fix (TF)

The primary straight route segment for RNAV
The segment starts at either an Initial Fix (IF), or the termination of a previous segment.

Direct to a Fix (DF)

Defines a route segment from an unspecified aircraft present position to a specified fix/waypoint.

Course to an Altitude (CA)

Defines an outbound route segment that terminates at an altitude, not at a specific location.

Heading to an Altitude (VA)

Defines an outbound route segment that terminates at an altitude, not at a specific location
Similar to Course to Altitude (CA), but fly an uncorrected heading without regard to wind or ground track.

Course to  a Fix (CF)

Defines a wind-corrected course to a specific fix
Frequently used as the final segment of an approach

Course from a Fix to an Altitude (FA)

Segment begins at a defined fix/waypoint
Requires a wind-corrected heading to maintain course
Terminates when the aircraft reaches the assigned altitude, not a specific location
Common in missed approach procedures.

Others:

Course from a Fix to a Manual Termination (FM)
Heading to a Manual Termination (VM)
Heading to an Intercept (VI)
Constant Radius arc to a Fix (RF)

Every RNAV departure and approach is made up of a combination of the these paths and terminators.
King Schools has an online course for P-RNAV.