Execution is in simple terms, executing the idea perfectly solving that problem in an excellent manner at the end creating a WOW from your customer. It is relatively easy to come up with an idea, but execution is difficult because not every idea that seems simple in the beginning is so simple. You run into a lot of issues while implementing the idea, for example the battery you thought will last for 16 hours, turned out lasts only for 8 hours, so you figure out alternatives and fix your solution. It is relatively easy to do that in software because it is only matter of coding, which can be done relatively quickly than manufacturing.
Also execution typically involves a lot of Project Management activities, especially if you are developing something complex and new, you need to have the correct project management structure in place to make sure the initiative is done completely, herding the team, leading the team, keeping the team focussed on the end goal, they cannot digress and lose focus and go somewhere else, clearly define milestones, clearly define what needs to be done, clearly measure your progress, if plan A does not work, then have plan B, that is why the three key things for any software project is
1 - A thorough detailed specification
2 - A list of test conditions of every single scenario that is going to play out and
3 - A through understanding of what is requested from the developers as well the Business Analysts that are defining the processes or the system or the solution.
The larger the development team, the more project management work that is required. All this is part of execution.
Once the solution is developed, then selling,
What is the strategy to open doors with prospective customers?
Why would they buy?
What is in it for them?
What problem your idea is solving for them?
Why would why buy your product and not your competitors?
What about change management?
Are you selling to enterprises or consumers?
Then how are you going to scale?
What is your scaling strategy?
How can you accelerate adoption? etc -
that is all part of execution.
