notifyRecordUpdateAvailable in Salesforce Lightning Web Component is used to notify the Lightning Data Service that the record data has modified/changed on the server so that the Lightning Data Service can take the appropriate actions to keep wire adapters updated with the latest record data.

Sample Code:

Apex Class:

public class AccountController {
 
    @AuraEnabled
    public static void updateAccount( String strRecordId ) {
     
        update new Account(
            Id = strRecordId,
            Description = String.valueOf(
                System.now()
            )
        );
         
    }
     
}

Sample Lightning Web Component:

HTML:

<template>
    <lightning-card>
        <template if:true={isLoaded}>
            <lightning-spinner 
                alternative-text="Loading..." 
                variant="brand"
            ></lightning-spinner>
        </template>
        <div class="slds-var-p-around_medium">
        Name is {name}
        <br/><br/>
        Description is {description}
        <br/><br/><br/>
        <lightning-button
            label="Update Account"
            onclick={updateAccountRecord}
        ></lightning-button>
        </div>
    </lightning-card>
</template>

JavaScript:

import { LightningElement, wire, api } from 'lwc';
import { 
    getRecord, 
    notifyRecordUpdateAvailable, 
    getFieldValue 
} from 'lightning/uiRecordApi';
import updateAccount from '@salesforce/apex/AccountController.updateAccount';
import ACCOUNT_NAME from "@salesforce/schema/Account.Name";
import ACCOUNT_DESCRIPTION from "@salesforce/schema/Account.Description";
import { ShowToastEvent } from 'lightning/platformShowToastEvent';

export default class AccountUpdate extends LightningElement {

    @api recordId;
    name;
    description;
    isLoaded = false;

    @wire( getRecord, {
        recordId: '$recordId',
        fields: [ ACCOUNT_NAME, ACCOUNT_DESCRIPTION ]
    } )
    wiredRecord( { error, data } ) {

        if ( error ) {

            console.log(
                'Inside error block'
            );
            let message = 'Unknown error';

            if ( Array.isArray( error.body ) ) {

                message = error.body.map(e => e.message).join(', ');

            } else if ( typeof error.body.message === 'string' ) {

                message = error.body.message;

            }

            this.dispatchEvent(
                new ShowToastEvent( {
                    title: 'Some error occurred',
                    message,
                    variant: 'error',
                } ),
            );

        } else if ( data ) {

            console.log(
                'Data is',
                JSON.stringify( 
                    data
                )
            );
            this.name = getFieldValue( 
                data, 
                ACCOUNT_NAME 
            );
            this.description = getFieldValue( 
                data, 
                ACCOUNT_DESCRIPTION
            );

        }

    }

    async updateAccountRecord() {

        this.isLoaded = true; 
        await updateAccount( 
            { strRecordId : this.recordId }
        );
        await notifyRecordUpdateAvailable( 
            [ { recordId: this.recordId } ] 
        );
        this.isLoaded = false;

    }

}

js-meta.xml:

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>58.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__RecordPage</target>
    </targets>
    <targetConfigs>
        <targetConfig targets="lightning__RecordPage">
            <supportedFormFactors>
                <supportedFormFactor type="Large" /> 
                <supportedFormFactor type="Small" />
            </supportedFormFactors>
        </targetConfig>
    </targetConfigs>
</LightningComponentBundle>

Output: