I searched sac1 in uniprot to know more about this gene. in interaction I selected this link and there I see that this gene has some "physical interactions" and "genetic interactions". I am wondering that what is the difference between "physical interaction" and "genetic interaction"?
Physical and genetic interactions are described in the help wiki, accessed via the top menu bar on the page you linked to.
Physical interactions refer to experiments where the gene product (protein) has been shown to physically interact with another protein, such as by co-immunoprecipitation, fluorescent staining, yeast two-hybrid system, etc.
Genetic interactions refer to experiments where changes in a certain gene reflect in changes to your gene of interest (or vice-versa) - dosage lethality, dosage rescue, synthetic haploinsufficiency, etc.