(rather short-term, ie some months to three years, contract and social security as far as possible abroad and intended return to origin)
The Senior or Specialist worker visa is a subset of the wider Global Business Mobility route, which allows overseas employers to transfer their employees to the UK branch or subsidiary to undertake a skilled role (defined as RQF 6). The employee must meet the higher of the general salary threshold of £48,500 per year or the going rate for the role. The employee must have worked for the overseas entity for at least 12 months, unless the individual is classified as a high earner. There is no English language requirement. The maximum visa duration is capped at five years in any six-year period under the Global Business Mobility routes unless a high earner. The employer must have a sponsor licence in the Global Business Mobility (Senior or Specialist Worker) category. This route does not lead to settlement.
(rather long-term or indefinite, local contract and social security)
The Skilled Worker visa is used for local permanent hires. The individual must have a job offer from an employer who has a sponsor licence in the Skilled Worker category. The role must be skilled to RQF 3, which is lower than the level required under the GBM (Senior or Specialist Worker) visa. In most cases, the individual must satisfy the higher of the general salary threshold of £38,700 per year or the going rate for the role. An employer is permitted to pay a lower salary under the tradeable points table if the requirements are met (e.g. the job is on the Immigration Salary List, new entrants). The individual must also satisfy the English language requirement, which might involve taking an approved test or using a foreign degree for verification (if it was taught in English). The Skilled Worker visa route leads to settlement in the UK after five continuous years of residence.