Change your preferences here.
Deals damage and has a 100% chance to lower the target's Speed by one stage.
Electroweb's Base Power and accuracy are rather poor by competitive standards, but its secondary effect makes the move somewhat useful. Some Pokemon that are weak to revenge killers can use this move to catch a switch in, reducing its Speed by one stage and thus averting the danger. However, this strategy is not commonly seen since it is unreliable.
However, it's a different story completely for Electroweb in doubles and triples. Being able to slow down both or all of the opponent's Pokemon in one turn can easily open up a sweep for a teammate. Unfortunately, Electroweb lacks any notable users of the move as most of the Pokemon that learn it should be filling an offensive role, if any role at all. One Pokemon that could work is Porygon2 thanks to its massive bulk and large support movepool, with which it can easily cripple the opponent multiple times with Electroweb and will have multiple tries to use the move even if you mispredict the opponent's Protect or if it misses.
Icy Wind is an Ice-type equivalent.