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Question on free command

I have two questions on Linux's free command. Below, I have provided output from my home laptop (fedora 26 ) which has 16GB Physical RAM and an enterprise production server (RHEL 7.4) which has 24GB RAM.

Question1. What exactly does the buffer/cache column say in free command's output ? buffer/cache is only 1GB in my home laptop but it is 18GB in production server below.

Question2. To know the free RAM available to the system, Can I trust the 'available' column rather than the 'free' column ? In my home laptop, the 'free' column shows 13GB and available shows 14GB But, in my production server, when the free command shows just 2GB , the available command shows 9 GB

free command's output from my Dell Home Laptop with 16 GB RAM (Fedora 26)

[sysadmin@johnspc ~]$ cat /etc/redhat-release
Fedora release 26 (Twenty Six)
[sysadmin@johnspc ~]$
[sysadmin@johnspc ~]$ uname -a
Linux johnspc 4.12.8-300.fc26.x86_64 #1 SMP Thu Aug 17 15:30:20 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
[sysadmin@johnspc ~]$
[sysadmin@johnspc ~]$ free -h
              total        used        free      shared  buff/cache   available
Mem:            15G        854M         13G        385M        1.0G         14G
Swap:          7.8G          0B        7.8G
[sysadmin@johnspc ~]$
[sysadmin@johnspc ~]$ free -m
              total        used        free      shared  buff/cache   available
Mem:          15939         854       14073         385        1011       14362
Swap:          8034           0        8034
[sysadmin@johnspc ~]$

A production Server (VM) with 24GB RAM (RHEL 7.4)

[root@hewdbprod218 ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.4 (Maipo)
[root@hewdbprod218 ~]#
[root@hewdbprod218 ~]# uname -a
Linux hewdbprod218 3.10.0-693.5.2.el7.x86_64 #1 SMP Fri Oct 13 10:46:25 EDT 2017 x86_64 x86_64 x86_64 GNU/Linux
[root@hewdbprod218 ~]#
[root@hewdbprod218 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:            23G        3.3G        2.0G         10G         18G        9.0G
Swap:          2.0G        1.4G        674M
[root@hewdbprod218 ~]#
[root@hewdbprod218 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:          23948        3471        2002       11006       18473        9194
Swap:          2063        1389         674
[root@hewdbprod218 ~]#