They are transformers. They are characterized to work at higher frequencies than power transformers. They are used for coupling and impedance matching.
"For radio frequency use, transformers are sometimes made from configurations of transmission line, sometimes bifilar or coaxial cable, wound around ferrite or other types of core. This style of transformer gives an extremely wide bandwidth but only a limited number of ratios (such as 1:9, 1:4 or 1:2) can be achieved with this technique.
The core material increases the inductance dramatically, thereby raising its Q factor. The cores of such transformers help improve performance at the lower frequency end of the band. RF transformers sometimes used a third coil (called a tickler winding) to inject feedback into an earlier (detector) stage in antique regenerative radio receivers."
and i might add wide band rf trannys application are for matching impedance, voltage/current transformation, dc isolation, power splitting, signal inversion, likewise balance/unbalanced mixing.
there's this custom wide band trannys that has special combination of impedance ratio, also frequency response, just to mention a few.
you should also check the very informative tutorial in this site.