when 1 object  slides over another object the1st  object doesnot  get enough time 2  lock  into  the  other  object  so  sliding friction is less than static friction .

 when a box start sliding <the contact point of the irregularities do not get enough time to lock between the surface of The floor. That is why sliding friction is less than static friction tht is why u will find it easier to pull a box in motion than 2 get it started. nnnnnnnnnnn 1 thing is also i didnt hav copied this from pratiksha is cumin in my exams.

 the force required to overcome friction at the instant an object starts moving rest is a measure of static friction.on the other hand ,the force required to keep the object moving with the same speed is a measure of sliding friction .when the box starts sliding the contact point on its surface, do not get enough time to lock into the contacts points on the floor.so,the sliding friction is slightly smaller than the static friction.