Wat is Convolutional neural network?

A convolutional neural network applies the same small filter at every position of its input: a one-dimensional convolutional layer maps a sequence $z_1,\dots,z_T$ of $d$-vectors to $u_t = \mathrm{act}(\sum_{j=0}^{k-1}B_jz_{t+j-\lfloor k/2\rfloor} + c)$, with $k$ filter matrices $B_j$ shared across $t$.