What are project deliverables in everyday terms? I’m having a hard time grasping the concept.

They are normally considered to be the items that the project produces. They are often physical items, but they could be items like “a 10% increase in sales”.

External deliverables are those requiring customer buy-off, normally at the end of the project. e.g. the completed building, the new design being delivered, the 20 widgets you’ve made, or a new piece of software. Internal deliverables are items created along the way (e.g. project management plan, requirements document, preliminary design). These are important, but not really what the customer is paying for.

Deliverables should be measurable and/or quantifiable. If you just define a Deliverable as “an increase in sales”, people are likely to debate whether that means 1% or 10%. Don’t forget Deliverables such as documentation, training manuals, maintenance plans etc. that are often critical to project success, but are often overlooked when Deliverables are being defined.