It is simple english combined with basic navigation.
If you are flying a heading, you will drift depending on the wind. With a crosswind heading and track are different.
When sitting on the threshold, you can be told 1 of 3 things;
1. Fly straight ahead. Look out your window down the extended runway centerline and have a think about what heading you are going to have to fly in order for the aircraft to proceed straight ahead. Hint - in a crosswind it will not be the same as the runway heading.
2. Fly Runway Heading. Look at the chart and it will tell you what the runway heading is. Fly that heading. Simple. Since one is expected to keep the heading within 5deg and the runway number will be 5 deg or less from the actual heading, then either will do the same job but the actual heading is the most accurate.
3. Track Runway Centerline. Use basic navigation to ensure that the heading you fly causes the aircraft to track along the extended runway centerline. Gain simple.
PANS-OPS Part 1 is very clear that pilots should fly tracks when they are specified making an appropriate allowance for the wind but when being radar vectored no allowance for wind is made by the pilot.
It is also very clear that pilots should not accept radar vectors until clear of obstacles. To me that means that give a clearance of fly runway heading or fly xxx heading after departure, I will track the runway centerline until the minimum turn height for that aerodrome and then fly the assigned heading. That prevents my aircraft from drifting into close-in obstacles which can be a problem during strong crosswinds with a slow aircraft and lift-off well before the departure end of the runway.
Regards,
DFC