how can I remove my actual OS, which is 4.4.0-142-lowlatency?
It is not an OS: only a kernel. You can remove
"linux-image-4.4.0-142-lowlatency" and "linux-image-lowlatency" (and
"linux-lowlatency", if installed) with your favorite mean to manage your
packages. Maybe you like the "Synaptic Package Manager"? If so:
launch it;
right-click on the installed packages you want to remove (you can "search"
them first);
click on "Mark for Complete Removal" in the contextual menu that pops up;
Click on the "Apply" button;
Confirm the complete removal by clicking on (another) "Apply" button.
See https://trisquel.info/en/wiki/installing-updating-and-removing-software
but the way, what does lowlatency mean, is there any relation about music
creation?
It refers to a different configuration of the kernel. If you do not have
special needs (like music artists working on computers, who often need a low
latency), then you want a "generic" kernel.
what is linux-lowlatency-hwe-8.0, what are the differences?
Trisquel is a stable GNU/Linux distribution: except for Abrowser, the
packages in a given version of Trisquel only receive security updates or
critical bug fixes. In particular, since Trisquel 8 shipped with a 4.4
kernel, it is still that version of the kernel that is the default. It
received many security updates though: 142, apparently.
The problem is: a 4.4 kernel may not properly support (or at all) brand new
hardware. In particular, hardware that started to be sold after 2016,
because Linux 4.4 was released in 2016. "hwe" stands for "HardWare
Enablement". Those are packages providing more recent versions of packages
that are important to support more recent hardware: like the kernel and the X
server. Installing "linux-image-generic-hwe-8.0" actually provides what will
be Trisquel 9's kernel, based on Linux 4.15, released last year.
