Sleep

Explanation
The sleep function will pause the execution of the game for numb milliseconds (there are 1,000 milliseconds in a second so to pause the game for a second you should use a value of 1000). Nothing will happen when the game sleeps, except that music continues playing. No instances move and there is no reaction to user interaction.

Examples
Sleep is typically used to draw attention to an important event. For example when the character dies or when you complete a level. The following example checks whether there are no more monsters and if so, plays a winning sound, sleeps a while and then moves to the next room.

if (instance_number(obj_monster) == 0) {    sound_play(snd_won); sleep(1000); room_goto_next; }

You should place this in the step event of some controller object or the main character in the game.