How to interpret this error in dmesg and what to do after that?

How to interpret this error in dmesg and what to do after that?

I run dmesg and this is what I see:
EXT4-fs (sda1): warning: mounting fs with errors, running e2fsck is
recommended
EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts:
Here is the stuff in context
EXT3-fs (sdd1): using internal journal
EXT3-fs (sdd1): mounted filesystem with ordered data mode
EXT4-fs (sda1): warning: mounting fs with errors, running e2fsck is
recommended
EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts:
EXT4-fs (sdb1): warning: maximal mount count reached, running e2fsck is
recommended
EXT4-fs (sdb1): mounted filesystem with ordered data mode. Opts:
EXT4-fs (sdc1): warning: maximal mount count reached, running e2fsck is
recommended
EXT4-fs (sdc1): mounted filesystem with ordered data mode. Opts:
Adding 4194296k swap on /dev/sdd2. Priority:-1 extents:1 across:4194296k SSD
kjournald starting. Commit interval 5 seconds
EXT3-fs (loop0): warning: maximal mount count reached, running e2fsck is
recommended
EXT3-fs (loop0): using internal journal
EXT3-fs (loop0): mounted filesystem with ordered data mode
what is e2fsck anyway? How to run it?