What did you do this summer?
If you did something productive this summer like research or internships and are planning to apply to grad school this cycle, you should be sure the experience is appropriately documented on your resume. Internships are one way admissions committees differentiate between applicants on the professional side of an application.
Adcoms like to see both quantity and quality, but when the quantity is low, internships get much closer scrutiny. Be sure they are listed clearly and describe the work well. The litmus test is whether you consider the experience professional enough to put on the resume. If it is on the resume, it will get looked at and is therefore a contributor to your application.
Generally, adcoms don’t care what format your resume or cv is in and we see wide variations between candidates. Once at a business or professional school, you should expect to rewrite your resume in optimal format for the industry you are planning to work for so it doesn’t already have to be in that format. If a school does require the resume in a specific format or imposes a length limitation, respect that and follow their guidance closely.