The phrase is used as one, and the two words carry different consequences.
A representation is a statement of existing fact made to induce the other party to contract. A false one can support a misrepresentation claim, which sounds in tort, may allow rescission, and can reach beyond the contract’s limitation clauses.
A warranty is a contractual promise that a state of affairs is or will be true. Breach gives a contract claim for damages measured by the difference between the promised and actual position.
Practical consequences:
Reliance. A misrepresentation claim generally requires reliance; a warranty claim generally does not. That matters when a buyer discovers a problem during diligence and closes anyway.
Knowledge qualifiers. “To the seller’s knowledge” narrows a statement considerably, and whose knowledge counts — and whether inquiry is required — should be defined.
Survival. Warranties typically survive closing for a stated period; after it they cannot be claimed on. Fraud is usually carved out of every limitation.
Materiality and baskets. Thresholds below which no claim may be brought, and whether they are deductible or first-dollar once crossed.