Sorry about being a newbie at this
No problem, everyone of us was at one point. Welcome to the board.
On a rough note, could one say that cardioid mics are for outdoor big concerts, stadiums and the like, and binaural mics are for smaller venues?
No.
First a few basic definitions-
As stated by others,
cardioids are directional mics. They have a pickup pattern that is most sensitive to sound in the front half of the microphone and progressively less sensitive to sound that approaches from the back half the microphone.
Omnidirectional mics are equally sensitive to sound in all directions. In reality they become somewhat directional at high frequencies depending on the size of the mic, but not nearly as much as a cardioid pattern.
Binaural mics are nothing but small omnidirectionals. You will also sometimes hear them referred to as
lavaliere mics. Those omnis are so small that they do not become directional until very high frequencies, often so high that they are close to perfectly omnidirectional.
Now for a few words on typical usage and opinions-
All things being equal, omnis can often sound more natural than cardioids for a few reasons I won't go into here. But of course all things are rarely equal. Your question simplifies things a bit too much, but in someways exactly the opposite is true: omnis are often a great choice for big outdoor venues and cardioids can often be a better choice for recording in small rooms and less than ideal situations. But that's way over simplifying things and isn't always true.
Great recordings can be made with both types of microphone, but they require different techniques and approaches. Generally, a number of factors including the recording situation, the performance space and the type of music are all important to consider when determining which technique to use. The choice of a particular technique then determines which type of microphone is appropriate. There are no hard and fast rules as to which is best. It really depends on the recording situation, what qualities you value most in your recordings and which techniques you prefer to use to get there.
Spend some time exploring the site and you'll find plenty of information on various techniques and appropriate mic types for your recording situation and goals. Try to get a feel for general trends of use instead of accepting the first answer you come across. Read critically and be on the lookout for opinions masquerading as facts. Then make a lot of recordings and play with the variables and develop your own opinions.
Then we can argue about them and have fun defending our personal sacred cows.