Loss and expense is the money side of employer-caused delay and disruption: the contractor’s entitlement to be reimbursed costs it would not otherwise have incurred, such as extended preliminaries, standing plant and lost productivity.
Unlike an EOT, which moves a date, loss and expense must be proved as actual loss with records: what was spent, why, and how it flows from the event complained of. Global claims that bundle everything together without that linkage are routinely cut down.
Disruption is the hardest head to prove because it is about productivity, not just time. Day-by-day records of gangs, work fronts, access and output are what make a disruption claim measurable rather than rhetorical.