AxisTensors have no documentation

[Sbozzolo]

Searching axistensors in the docs

Searching in the code base gives a little more

"""
    AxisTensor(axes, components)

An `AxisTensor` is a wrapper around a `StaticArray`, where each dimension is
labelled with an [`AbstractAxis`](@ref). These axes must be consistent for
operations such as addition or subtraction, or be dual to each other for
operations such as multiplication.


# See also
[`components`](@ref) to obtain the underlying array.
"""

this is not enough to understand what they are for and how to use them

[valentinaschueller]

The same seems to be the case for FieldVector: Not part of the Fields API documentation but there seems to be in-code documentation.