Although these terms are often used interchangeably:
wage = salario
salary = sueldo

Wage/salario is paid by unit of time worked, usually by the hour. If you draw wages (salario), you usually know how much you make per hour.

Salary/sueldo is paid after a stipulated work period, often every two weeks or at the end of the month, but if you are paid a salary (sueldo), you don’t know your hourly pay rate.

(In this sense, and strictly speaking, salary and salario are “false friends”) See the following references:

What is the difference between wages and salary?
You should be aware that some people use the terms wages and salary interchangeably. I and many others make the following distinction.

Wages is best associated with employee compensation based on the number of hours worked multiplied by an hourly rate of pay. For example, an employee working in an assembly plant might work 40 hours during the work week. If the person's hourly rate of pay is $15, the employee will receive a paycheck showing gross wages of $600 (40 x $15). If the employee had worked only 30 hours during that week, her or his paycheck will show gross wages of $450 (30 x $15). Because the paycheck needs to be computed based on the actual hours worked, the employee earning wages will likely receive her or his paycheck five days after the work period.

Salary is best associated with employee compensation quoted on an annual basis. For example, the manager of the assembly plan might earn a salary of $120,000 per year. If the salaried manager is paid semi-monthly (perhaps on the 15th and last day of each month), her or his paycheck will show gross salary of $5,000 for the half-month. Since the salary is the same amount for each pay period, the salaried employee's paycheck will likely cover the work period through the date of the paycheck.
https://www.accountingcoach.com/blog/wages-salaries

Diferencia entre sueldo y salario
Tanto sueldo como salario se refieren a la remuneración que un profesional o trabajador recibe de parte de un empleador a cambio de su trabajo o sus servicios.
No obstante, sueldo y salario no son sinónimos exactos y conviene distinguirlos cuando se está hablando de nóminas de empleados y sistemas de retribución para la contabilidad de una empresa.
El sueldo es la remuneración o paga fija que, de manera regular, percibe una persona por parte de un empleador por el desempeño de un cargo o servicio durante un tiempo determinado.
Como tal, es una cantidad fija, previamente acordada por ambas partes, que es pagada periódicamente al trabajador, bien de manera semanal, quincenal o mensual.
En este sentido, el sueldo no está sujeto a descuentos por días festivos y no variará si un mes hay menos días laborables que otro.
El salario, por su parte, es la paga o retribución monetaria que un trabajador recibe a cambio de sus servicios. A diferencia del sueldo, el salario es calculado con base en días u horas de trabajo, de modo que es fijado por unidad de tiempo.
Un trabajador que trabaja por horas o por días recibe un salario que podrá variar en función de la cantidad de horas o días que trabaje. En este sentido, el salario no es, como el sueldo, una paga fija que se recibe de manera semanal, quincenal o mensual, sino una retribución. https://www.significados.com/diferencia-entre-sueldo-y-salar...