Automotive, or SLI (starting, lighting & ignition)
SLI batteries are commonly used to start and run automobiles, where a very large starting current is needed for a short time. SLI batteries have many very thin plates with a large surface area, designed to be discharged no more than 1 to 5% from full charge. These can be damaged quickly if deep cycled.
Marine / Deep Cycle
Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates.
The so-called Marine deep-cycle batteries are actually a "hybrid", and fall between the SLI and deep-cycle batteries. These should not be discharged more than 50%. SLI batteries are usually rated at "CCA", or cold cranking amps, or "MCA, Marine cranking amps". Any battery with the capacity shown in "cranking amps" is NOT a deep-cycle battery, and some marine batteries with MCA ratings may be a hybrid (basically a battery with thicker plates than an automotive battery, but thinner than a true deep-cycle).
Nay... that pretty much sums it up:
Just make sure the battery you have/buying has the minimum cranking amps for the engine connected? They are different from each manufacture, including the big names!
I would suggest a "marine battery" as they do have thicker plates... and most on here would want/need a Group 24, some a Group 27, very few a Group 31?.