>>11612310RNA has a 2' hydroxyl, an -OH, on the ribose sugar. this makes it more reactive, less stable, and allows for more secondary structures to form such as hairpins, loops, etc. instead of thymine there is a uracil.
The reactivity is a big part of the "RNA world" hypothesis. Things like ribosomes have all their functional domains made of RNA with the protein regions mostly providing structure/stability.
The secondary structure is the thing. If you wanna see something neat look up SELEX, it's a selection procedure for developing RNA sequences that have extremely high binding affinity for a given protein, domain, etc.
