Remasters - are they better? What exactly is it?

The idea behind remastering is to take the original master tapes and get a better transfer to the tapes (analog) or files (digital) that are going to be used by the pressing plants to make LPs or CDs.

Many things can and often do go awry though. The wrong tapes are used (a later generation of tapes than the master tapes, etc., a little resolution is lost each time a tape is copied). The mastering engineer may decide to make changes to the sound, boost the bass a little, for example. Sometimes the tapes have degraded since the original mastering was done.

The biggest problem is that many remasters are overly compressed. Quieter sounds are made louder. Loud sounds are made so loud that the loudest peaks of sounds are chopped off. The dynamic range (the difference between the quietest and loudest parts of a song) is lessened. In the worst cases, once enjoyable albums are turned into one loud in-your-face endurance test. This is a oversimplification of remastering, maybe someone who knows more about the process can explain better.

Yeah, ok so...  I cannot find any older recording (50s 60s 70s and most 80s) that dig that low or that have "involving" bass like you might hear from albums by Celtic Women, Hans Zimmer, Celine Dion, Adele, etc.  

Those albums will really test a subwoofer.  When I crank up a Rolling Stones, I feel the sound is thinner or more shrill.. Like it was recorded as cheaply as possible and it's just not "rock" feeling (in general).

It seems like newer recordings are much fatter/fuller, crisp/detailed, and present.

Also, listening to old Bob Dylan albums, the guitar is nowhere near as "wow that's nice sounding" as say Mumford and Sons or John Mayer.

Recording equipment has improved since the 60s and really good modern recordings can be made these days. The cd is capable of much stronger bass than the LP. Digital files can be played and copied many times without losing detail. That doesn’t have anything to do with remastering, though. The Stones early stuff is in general pretty badly recorded.

People who enjoy classical and jazz recording techniques from the 50s and 60s will tell us that those techniques and the albums are far superior to modern techniques. Much more natural and realistic.  As always YMMV.

Compression is just a small part of the process and is more a sign of the times in general than just of remastering. The rise of compression since the mid 90s can effect all releases whether remasters or new issues.