Gross motor skills are those abilities related to movement of the large muscles of the body (unlike fine motor skills which are controlled by the small muscles).
In human development, gross motor skills are generally learned sooner in life and with greater ease than fine motor skills. However, gross motor skills like catching a ball or jumping rope that can involve complex timing and planning may remain difficult for some individuals into adolescence or adulthood.
People with good gross motor skills often enjoy and excel at sports, whereas people (like me) with poor gross motor skills have difficulty playing sports and thus may have difficulty socially in elementary school!