Here we translate all this stuff into more common language.
So simple tiume signature create straight grooves and shuffle use compund time signatures. Let's look at that a little more closely.
A straight groove is straight because your foot taps straight up and down evenly and every notes either fall on a downbeat or an upbeat, or evenly in the space between. In practice we usually have two types of straight grooves, 8 to the bar straight Rock grooves and 16th note funk grooves. That's not to say that other styles of music don't use these feels but eight to the bar tends to define rock and roll (think Chuck Berry) in the same way that 16th notes grooves define funk (think James Brown). Listen to both of these guys, find the drums and focus in on the hi-hat. You'll hear either eight or sixteen in every bar.
Remember that a 12/8 bar has four beats, each divided into three. It becomes a shuffle when the first two in each beat are joined together. So instead of playing 123 123 123 123, you play 1_3 1_3 1_3. Once you've heard it it'll make sense. !2/8 blues tend to be slower while shuffles usually have a faster tempo.
The best thing to do here is listen to the masters..
|8 to the bar||16th groove||12/8||Shuffle|
|Rock and Roll Music - Chuck Berry||Too Funky in here - James Brown||Everybody wants to go to Heaven - Albert King||Further on up the Road - Bobby Bland|
|Hound Dog - Elvis Presley||So Damn Good - Jon Cleary||Sweet Sixteen - B B King||Caldonia - B B King|
|Give me back my wig - Hound Dog Taylor||Fat Man in the Bathtub - Little Feat||Sitting on top of the World - Howlin' Wolf||Highway 49 - Howlin Wolf|
|Satisfaction - The Rolling Stones||Shake for Me - Howlin' Wolf||Double Trouble - Muddy Waters||This is Hip - John Lee Hooker|
|Let It Be - The Beatles||Born Under a Bad Sign - Albert King||Something on your Mind - James Cotton||The Sky is Crying - Elmore James|
|Good Morning Little Schoolgirl - Muddy Waters||Tiger in your Tank - Muddy Waters||Blueberry Hill - Fats Domino||Bring it on Home - Sonny Boy Williamson|
|Diddy wah diddy - Blind Blake||Terraplane Blues - Robert Johnson||Texas Flood - Stevie Ray Vaughan||Wine spodee odee - Lightning Hopkins|
|Candy Man - Mississippi John Hurt||Me and Julio down by the School Yard - Paul Simon||I Can't Quit You Baby - Otis Rush||Don't You Lie to me - Tampa Red|
|Lovesick Blues - Hank Williams||Kiss - Prince||Blues with a feeling - Paul Butterfield Blues Band||Heartbreak Hotel - Elvis Presley|
Listen to at least two songs from each column and hear how the groove fits the descriptions.