When you press F3

Java Version    The version of the Java (eg: 1.8.0_74 64 bit)
Memory    Amount of available memory, depending on your device.
Allocated Memory    The memory that cannot be changed
CPU    Central Processing Unit, along with Intel/Core, along with GHz
Display    Shows display dimensions, along with graphics card stats
fps    The frequency at which frames in an electronic device consisting of a video game for instance, in which the video sequence is displayed. This is also referred to as frames per second (fps).
chunk updates
integrated server
C    Number of chunk sections
D    Reder Distance (client-based)
L    Blocks that have light updates to apply to (client-based)
pC    Pending chunks
pU    Pending uploads
aB    Available buffers
F    Number of loaded chunks outside the set render distance
O    Number of chunks terminated via occlusion culling.
E    Number of rendered entities over total entities in the form of a fraction
B    Unused, always zero
I    Amount of invisible entities
P    Quantity of particles onscreen
T    Shows your max frame rate and graphics type
All    Displays the amount of loaded entities (refer to entity list via /summon)
MultiplayerChunkCache    The highest number of chunks that can be loaded at a time.
Dimension FC    Location based on the dimension
XYZ    Location based on the coordinate scale. X: Number of blocks east or west, Y: Altitude and Z: Number of blocks north or south
Block    Coordinates of the block a player stands on
Chunk    Location of a player within a 16x16 area (chunk)
Facing    The direction in which a player is facing.
Biome    Location of biome in a snake-case string. Invalid if a player is in the following parameters: y=..0, 255...
Client Light
Server Light
Local Difficulty
Looking At    Coordinates for looking at a block or fluid in the form of XYZ. This is always rounded to a whole number.```